K&B 3.5 3.5 Econo Power RC Engine Bearings K&B 3.5 3.5 (21CC) Econo Power RC Engine Bearings QTY. 1: R4-ZZC (0.2500x0.6250x0.6250 IN)  QTY. 1: MR6901-ZZC (12x24x24 MM)